Method and devices for driving a body

ABSTRACT

The invention relates to a method for relative driving of bodies on the basis of electromagnetic or piezo-electrical conversion of electricity into energy and/or movement. Use is made of intermediate bodies for the conversion into mechanical energy. The invention also relates to a linear drive assembly for a shaft or other elongate body, with engaging means for co-displacing engagement of the shaft and the like, as well as displacing means forming a moving whole with the engaging means for displacing the engaging means in driving direction between a non-engaging or slipping position and an engaging or shaft-co-displacing position. Means are further provided for displacing the displacing means in driving direction. In addition, the invention relates to a device comprising two drives assemblies according to the invention, wherein the drive assemblies are disposed for moving the shaft in opposite directions.

The present invention relates to a method for converting electricalenergy into mechanical energy. This conversion has the purpose, usingminimal assist means and provisions, of obtaining an actuator of thecorrect specifications at a favourable cost price. Particularlyenvisaged here is a linear or rotational actuator, which can be providedwith power supply via simple electricity cables and which can producethe required displacement or force without other means.

In the current practice of mechanical engineering and motion technologythere are different solutions for the different driving problems.Broadly speaking, the classes of available drive systems are hydraulic,pneumatic and/or electromagnetic drives.

In hydraulics there is the problem of the use of oil, which is oftenconsidered undesirable for environmental reasons. A further drawback isthe low efficiency (<50%), while on the other hand it has a very highenergy density. Very great forces can also be achieved herewith inrelatively simple manner.

In pneumatics use is made of compressed air to drive cylinders. Thenecessity for a compressed air provision is a great drawback here. Sucha provision is already available at many industrial locations, but it isvery expensive (also in use). The particular necessity of obtaining suchan installation and (per machine) the accessories for air treatmentmakes large demands on the budget. It has a low efficiency and producesmuch noise nuisance. The venting of air which still contains oil alsoforms a problem in different branches of industry, such as the medicalindustry, food industry, printing industry, textile industry and thelike.

In electromechanical motion technology there are many types of drivewhich are very well suited for a plurality of applications. In the‘lower segment’ of the market however, there is no advantageous solutionfor the frequently occurring ‘direct-drive’ requirements of industry.‘Pick and place’ applications and adjustment options can be envisagedhere. Much applied for this purpose is pneumatics using a fixed stop,which produces two positions. The spindle drive is also a very commonone. This latter is a relatively expensive solution.

In respect of minimizing the economic and ecological cost of the use ofactuators, an actuator is sought with a high efficiency and a low costprice. The present invention has for its object to enable the productionat this low cost price of an actuator with a low ecological impact. Thesolution must be reliable and inexpensive, in addition to which it mustcomply with reasonable specifications. It is important for this purposethat the solution is simple, whereby the reliability and the low costprice can be combined.

The low cost price results from the use of relatively simple means,though in a manner whereby relatively high performance can be achievedtherewith. An example hereof is the use of simple clamping mechanismsfor fixing the intermediate bodies and the body for driving, forinstance a drive shaft. These can be produced in simple and inexpensivemanner and exhibit hardly any hysteresis in their operation. This ispartly due to a relatively great rigidity, whereby less step lossoccurs, and the fact that no relative movements are allowed at themoment of force transmission. Two types of these clamping mechanisms canbe distinguished, viz. unilateral clamping and bilateral clamping.

Further advantage is achieved from buffering energy, whereby energysupply can be performed intermittently and efficiently while emissiontakes place uniformly. For this purpose the current transmission throughthe coils of an electromagnetic converter can be limited to a peak oflimited height and width.

The invention also provides a method whereby the electrically generatedforce contains both an active and a reactive force. It is herebypossible during charging of one of the buffers to have the forceproduced by this buffer to be temporarily produced by an adjacentintermediate body. A more uniform force and speed profile is herebyobtained with a higher efficiency. Owing to the invention this forcecoupling is also such that the mechanism continues to operate in thesame manner, without being influenced by the position relative to thehousing. This is possible because a coil is fixed in the housing andbecause the force-generating gap between two intermediate bodies isfreely movable relative to the coil. In the case of a piezo-actuation,the piezo-element will exert a force between both bodies, without theposition relative to the housing having to be fixed hereby. A higherefficiency can be achieved by this (relative) driving not dependent onposition.

A variety of forms are possible as embodiments of the actuator describedin this invention. A linear actuator with the outward appearance of apneumatic cylinder can be envisaged. This takes a slender form for thetime being. But the principle also lends itself for an embodiment in ashorter version with a larger diameter.

In the rotational variant a choice can also be made between a longversion with small diameter and vice versa. The rotational variant isparticularly suitable where relatively large torques are required atrelatively low powers and speeds. This ‘direct-drive’ actuator is highlysuitable here owing to a compact installation and the absence of areductor.

At the moment that two (or more) intermediate bodies make a movementrelative to each other, in the case of unidirectional blocking the oneintermediate body will make a relative movement relative to the body fordriving, while conversely the other intermediate body will co-displaceit. When the relative movement is reversed, this will take place theother way round. Using the energy buffering, both these intermediatebodies will as it were charge themselves and ultimately relinquish thisenergy to the body for driving.

In the case of a bilateral clamping mechanism, the control will ensurethat the choice for co-displacing the body for driving and the relativemovement take place in a manner and with a timing such that a uniformmovement and efficient force transfer will take place.

The present invention has for its object to provide a method of the typedescribed in claims 1 and following, whereby it is possible to supply aparticular market segment in motion technology with a low-cost actuator.

It is noted that a device as intended in U.S. Pat. No. 5,055,725 is notvery powerful because the total driving force can be drawn only from thediverted magnetic field. Nor are there intermediate bodies present. Theclamping mechanisms do not operate in the drive.

The tilting plate mentioned in patent GB 2 285 711 forms a whole and cantherefore not be used to buffer energy as in the present invention. Thesame applies to U.S. Pat. No. 5,315,202, which operates with the sameglue-clamp-like construction.

Patent DE 32 33 759 makes use of balls in a conical bush. This resultsin much hysteresis, whereby the efficiency of the utilized energybecomes very low. The clamping and driving principle are also bothembodied in this manner, each having available its own ‘drive coil’.

The mechanism in U.S. Pat. No. 3,445,689 is based on a pivoting movementabout a mounted shaft transversely of the direction of movement, wherebya plunger co-displaces a shaft situated therein under the influence of amagnetic force. This in contrast to the axial translations proposed bythis invention.

Finally, patent DE 43 29 163 is an invention based on the use ofpiezo-electrical driving. This embodiment does not however have anypossibility of allowing homogeneous movement of the body for driving,here a shaft. Nor is there any possibility of controlling speed orforce, and the clamping device described here is subject to wear andhysteresis.

The invention also relates to a linear drive assembly, and theinternational designation “Linear Shaft Driver” can also be applicable.

Linear drives are applied for displacing a shaft in a longitudinaldirection. Such a shaft can form a rigid body with which normal forcesfor driving another object are transferred. Another embodiment of such ashaft is that of a guide for an operating means. Usual linear drives, inparticular those operating hydraulically or pneumatically, are ratherbulky and/or susceptible to malfunction, and insufficiently precise dueto the displacement options of the components relative to each other,certainly after a period of time.

An object of the invention is to make improvements herein. In thesimplest embodiment the invention provides a fully controllable,double-acting linear drive on the basis of only two electromagnets.

In one aspect the invention provides for this purpose a linear driveassembly for a shaft or other elongate body, comprising engaging meansfor co-displacing engagement of the shaft and the like, as well asdisplacing means situated outside the shaft and forming a moving wholewith the engaging means for displacing the engaging means in drivingdirection between a non-engaging or slipping position and an engaging orshaft-co-displacing position, further comprising means for displacingthe displacing means in driving direction.

Such a drive can operate directly and is thereby accurate. The spaceoccupied can herein remain small. The displacing means are preferablyadapted to exert a pushing force on the engaging means in the drivingdirection, whereby engagement with the shaft can take place as quicklyas possible.

The engaging means preferably comprise shoes provided with engagingsurfaces which engage the shaft, as well as preferably resilient armswhich extend radially and counter to the driving direction of the shoesand which connect the shoes to the displacing means. By exerting a forceon the arms in driving direction, the pressing force of the shoes on theshaft will be greatly increased, whereafter the friction force of theshoes on the shaft is sufficiently strong for clamping co-displacementof the shaft by the shoes and thereby by the engaging means. The armsare herein preferably connected movably, in particular rotatably ortiltably, to the displacing means.

In order to speed up realization of the engaging contact of the shoeswith the shaft, it is advantageous if the shoes are at all times heldclose to the shaft by means of a revolving belt. The compactness of thedrive assembly and the reliability of operation are enhanced if thislatter is further preferably provided with an electromagnet forenergizing the displacing means. Energizing lines can herein be keptsimple, in particular be limited to electrical cables. The displacingmeans and drive means are herein preferably received in a holder, suchas a housing, which is disposed slidably in shaft direction. It can alsocomprise ferromagnetic material. In advantageous manner means can hereinbe present, preferably at least one electromagnet—or alternatively aspring—, for moving back the holder, in particular the displacing means,counter to the drive direction relative to the shaft.

In order to prevent a slide-back movement of the shaft, it isrecommended that the drive assembly is further provided with preferablystationary second means for retaining the shaft in a return movement,which retaining means preferably comprise shoes and arms comparable tothe drive means.

These retaining means preferably act passively on the shaft, whereinmeans are present for de-activating retaining means, preferablyelectromagnetic means.

In order to enhance the return movement of the drive assembly, it isrecommended that the means for de-activating comprise means for reducingthe contact pressure of the shoes against the shaft. In order to enabledriving in two directions, there is provided that the drive assemblycomprises two drive assemblies as described, wherein the driveassemblies are disposed for driving of the shaft in opposite directions.It is also recommended herein that means are provided for de-activatingthe displacing means, preferably electromagnetic means, during a returnstroke.

In another aspect the invention provides a linear drive assembly for ashaft or other elongate body, comprising engaging means forco-displacing engagement of the shaft and the like, further comprisingcontrollable (electromagnetically acting) means for displacing theengaging means in driving direction.

The drive assembly further preferably comprises controllable(electromagnetically acting) means for releasing the drive means fromthe shaft.

The drive assembly further preferably comprises controllable(electromagnetically acting) means for fixing the shaft.

Stated and other features of the method and devices of the inventionwill be further elucidated hereinbelow on the basis of a number ofembodiments. Reference is herein made to the drawings, in whichcorresponding components are designated with corresponding referencecodes, and in which:

FIG. 1 illustrates schematically a method with direction-dependentclamping mechanism and energy buffering;

FIG. 2 shows an embodiment wherein the automatic braking is trivial;

FIG. 3 shows an example of a bilateral clamping mechanism;

FIG. 4A shows energy-transmitting elements in the sliding position;

FIG. 4B shows energy-transmitting elements in the clamping position;

FIG. 4C shows an alternative form for the energy-transmitting elements;

FIG. 5 shows a longitudinal section through an exemplary embodiment of adrive assembly according to the invention;

FIG. 5A shows a detail 105 of a drive part in the assembly of FIG. 5;

FIGS. 6A-D show several schematic arrangements of a drive assemblyaccording to the invention for operation in one direction; and

FIGS. 7A-D show several schematic arrangements of a drive assemblyaccording to the invention for double action.

FIG. 1 shows the assembly of a shaft 10 enclosed by a housing consistingof a sleeve 12 and two closing flanges 13, 14. Inside this housing areplaced two or more intermediate bodies 20, 21, which are held in theirpreferred position by springs 25, 26. Situated inside the intermediatebodies is a direction-dependent clamping mechanism 23, 24 which isarranged acting in one direction by a setting mechanism 30. This settingmechanism 30 consists of two end plates 31, 32 which are held in apreferred position by a (cup) spring 33. In this position partly rigid34 and partly flexible 35 connections ensure that the force-transmittingelements 23, 24 come to lie in the correct position for their function.This position can be changed, for instance by a magnetic device 36 whichattracts end plate 32. The force-transmitting elements 23, 24 herebycome to lie in a different position (not shown here), whereby thedirection of movement is reversed.

Driving takes place by activating the coil 22 in pulsed manner, wherebythe intermediate bodies 20, 21 are drawn toward each other via themagnetic field and the gap therebetween is reduced. In FIG. 1, in theposition drawn therein, the intermediate body 20 will move to the right,whereby the springs 25 associated with this intermediate body will bebiased without shaft 10 hereby being influenced. During this action theintermediate body 21 will however be pulled to the left, whereby a forceis transmitted onto shaft 10 via clamping mechanism 24. After this pulsethe force for transmitting via intermediate body 21 will havedisappeared, but the position-dependent force of the bias in springs 25will transmit a remaining force onto shaft 10 via intermediate body 20.Due to the ending of the force on intermediate body 21 it will want tofall back into the preferred position in resonance. It will howeverovershoot due to the kinetic energy of the mass that is present, wherebya position-dependent force remains which is transmitted via clampingmechanism 24 to shaft 10. A high efficiency is hereby gained from briefactivation of coil 22. This principle can of course be expanded with aplurality of intermediate bodies and coils which are actuated in acorrect sequence and timing. A practically homogeneous movement, ordriving, will thus be created. In the case coil 22 is replaced by apiezo-element, a movement in opposite direction will result, whereby thefunctions of both intermediate bodies are exchanged.

FIG. 2 shows the method of a similar disposition, although there is inthis case a neutral position in the setting mechanism 30, whereby thedevice brakes automatically in both directions during power failure.When magnetic device 36 is activated the end plate 32 will be pulled tothe right, whereby the direction of movement of shaft 10 will be to theleft. This can be reversed by causing the magnetic device 37 to pull theend plate 31 to the left, whereby the direction of movement of shaft 10will be to the right.

FIG. 3 shows a bilateral clamping mechanism. Shaft 10 is clamped hereinby force-transmitting parts 40 which can be constructed from forinstance four segments of a bush which encloses the shaft. These partsare pressed onto the shaft by wire-spring elements 41, 42 since rings43, 44 are pressed axially apart under the influence of a spring 45. Avery high transmission ratio of this spring force hereby results, whichguarantees the clamping force on the shaft. Through the energizing ofcoil 46, the rings 43, 44 are however pulled toward each other. Owing tothe manner of embodiment intended by the invention, this takes place ina manner not dependent on position. Wire-spring elements 41, 42 willhereby have to lie in a so-called S-bend, whereby the radius of theforce-transmitting parts 40 will increase. These will hereby come tohang free of shaft 10, whereafter a relative movement between both parts10, 40 can be realized in simple manner. The position of the parts 40 ispreferably determined by springs 47, 48, whereby a position-dependentforce is generated. These springs must be embodied such that adifference in radius of force-transmitting parts 40 can be absorbedwithout friction. In addition, a force can be superimposed on theclamping body, for instance by energizing the coil 50 situated withinthe magnetic field formed by permanent magnet 51 and anchors 52, 53,whereby shaft 10 can driven either directly or indirectly.

FIG. 4 shows the tilting principle according to the invention. Presenthere as energy or force-transmitting elements (clamping mechanism 23,24) are elements which are placed between the shaft 10 for driving andan intermediate body 20, 21. These elements are characterized by ageometry which is such that, if these elements are placed with theheight of the cross-section perpendicularly of the shaft, there is asmall clearance between this element and the shaft (see FIG. A). Thisclearance ensures free axial movement of the shaft. These elements arepulled in a determined direction by means of setting mechanism 30. Thediagonal of these elements hereby becomes clamped between the shaft andthe intermediate body. This diagonal comes to lie such that an angle ais created, in which tan(α)<friction coefficient μ. Automatic brakinghereby occurs when the shaft is loaded with a force F_(I). Thecross-section of these tilting elements (compare 12 to 16) does not haveto be rectangular, but can for instance also be barrel-shaped, whereinboth boundary surfaces are flattened, thereby creating the above-statedclearance (see FIG. C).

The linear drive assembly shown in FIG. 5 comprises a housing 101 instationary position which encloses a shaft 102 for driving. Housing 101comprises two housing parts 103a, 103b which are fixed to each other.Herein formed in the centre is a chamber 104 in which a housing 105 isreceived. At the ends the housing 105 has walls 124 and 125 offerromagnetic material. These walls 124 and 125 can be mutuallyconnected by means of connecting parts 126, wherein connecting parts 126can also form an enclosing sleeve.

Placed in housing 105 at both longitudinal ends are electromagneticdecoupling coils 104 and 105, which are held at a fixed mutual distanceby means of spacer parts 110 to which they are fixed. The distance ofthe coils relative to the nearby situated end walls 124 and 125 isconstant. A radial clearance 113 is herein left between end walls 124,125 and coils 114, 115, in which clearance T-shaped ferromagneticanchors 120, 121 are received with their radial body. Clearances 113allow a small displacement of anchors 120, 121 in axial direction.

Between spacers 110 and coils 114, 115 are clamped the radial outer ends111 of drive parts 106, which are likewise substantially T-shaped with adrive shoe 108 located along shaft 102 and an arm 107 directed obliquelyradially outward and toward the nearby coil. Shoes 108 are provided withan engaging surface 109 and provided on their opposite surface with agroove 112, in which an assemble ring 150 (FIG. 5A) can be arranged. Theengaging parts 106 can together form an enclosing whole, for instancesuch as shown in FIG. 5A. They can further be manufactured from anysuitable material, such as for instance plastic.

Further arranged in housing 101, axially after the receiving space 104,are two drive coils 118, 119 fixedly mounted in housing 101, and axiallyoutside this another coil/drive part arrangement is then received atboth ends in housing 101, these arrangements being comparable to thoseof coils 114, 115 and associated drive parts.

Preferably mounted fixedly herein on the housing are decoupling coils116 and 117, which hold drive parts 106 d and 106 c fixedly clamped onhousing 101 and leave a small space on the axial outer side to slidablyreceive the radial arms of anchors 122 and 123.

It will be understood that the diverse coils are connected to a suitablepower supply and control means therefor.

When it is intended to move the shaft 102 in direction A, the drive coil119 is energized whereby the ferromagnetic end wall 125 is attracted andhousing 105 is thereby displaced in direction C. Coil 114 and the outerend 111 of arms 107 of engaging part 106 b are hereby also displaced indirection C. A tilting moment in direction F2 will hereby be exerted onarms 107, which will thereby come to lie more radially. As a result theshoe 108 with engaging surface 109 will begin to exert a holding forceon the surface of the shaft, and shaft 102 will immediately follow themovement of shoe 108, the 105 coil 114 and housing 105 in direction C,until end wall 125 moves against drive coil 119 or close thereto. Inthis movement the position of drive parts 106 a is not important sincethese co-displace in direction C. This is however not the case for driveparts 106 c since these are stationary with the housing. So as to enablea smooth transport of shaft 102 in the direction A, coil 117 isenergized during the movement of housing 105 in direction C, whereby theT-shaped anchor 123 is displaced in the direction opposite direction Aand then come to lie with the outer end of their horizontal legs againstshoes 108, whereby a slight tilting of the arms 107 thereof takes placein direction H and the engaging surfaces 109 of shoes 108 pressimperceptibly against surface 120 of shaft 102. When drive coil 119 isno longer energized, the energizing of coil 117 can also be stopped.

In order to drive the shaft 102 intermittently in the indicateddirection C, the housing 105 must then be moved back 125 in thedirection D. The shaft is herein held in place relative to housing 101by the shoes 108 of drive parts 106 d lying against the shaft on theleft-hand side of housing 101 as seen in the drawing. With an alreadyvery small movement of shaft 102 to the left, shoes 108 would also beco-displaced, whereby arms 107 tilt in the direction F1 and the pressingforce at the position of engaging surface 9 is increased.

When housing 105 moves in the direction D, shoes 108 of drive part 106 bcan slide to the left over the surface of shaft 102, although it isrecommended to then also energize the coil 114, whereby the T-shapedanchor 120 is moved to the right as seen in the drawing, and the arms107 of shoes 108 of drive parts 106 b are tilted in the direction F1 inorder to completely release the shaft 102. Coil 115 will in any casealso be energized in order to achieve the same effect, i.e. a tilting inthe direction G of arms 107 of drive parts 106A. Finally, housing 105again comes to lie in a position furthest to the left, and energizing ofcoils 114 and 115 can be stopped and the movement 110 of housing 105 inthe direction C can be started once again.

In this manner the shaft 102 can be displaced in direction A in veryrapid, pulsating manner. Operation of this drive assembly according tothe invention will be able to take place without disturbance through theuse of electromagnetic means. The size of the assembly can herein belimited. Great drive forces can also be achieved in simple manner. Inthe case of power failure and/or switched-off drive—also incalamities—the drive will be able to block immediately. Compared to theprior art the action of the drive assembly according to the invention isvery direct, and thereby safe and precise.

The drive assembly shown in FIG. 5 is suitable for double action. Inthat case the drive coil 118 is energized in order to attract theferromagnetic end wall 124 to cause housing 105 to displace in directionD, wherein the drive parts 106 a force the shaft 102 along in directionB with their shoes 108, and energizing of coil 116 via anchors 122slightly releases the shoes 108 of drive parts 106 d from the surface ofshaft 102. During the return movement, in this case to the right ofhousing 105, coil 117 is not energized to cause shoes 108 of drive parts106 c to perform a blocking action, and in any case coil 114, andpossibly also coil 115, can be energized again in order to prevent shaft102 being able to move back in the direction A.

With this arrangement a double-action linear drive is provided in verycompact manner.

FIG. 6A shows shaft 202 which can be driven in pulsating manner indirection B using a drive coil 219, which attracts a housing (notfurther shown) towards it in direction B, in which housing are arrangeddrive parts 206 a for direct co-displacement, as was the case in FIG. 5.The housing is tensioned in an opposite direction by means of springs240, so that the return movement of drive parts 206 a takes placeautomatically. On the left are also shown drive parts 206 d which arestationary and act as a clamping point to prevent the return movement ofshaft 202, if this is desired.

In FIG. 6B is shown a comparable arrangement wherein coils 214 and 216are however arranged close to drive parts 206 a and 206 d for the samereasons as in FIG. 5.

In FIG. 6C the assembly of drive part 206 a, coil 214 and drive coil 219is takes a double form, wherein it is possible to make provision for thecontrol and decoupling to take place in counter-phase for a more uniformoperation of shaft 202. FIG. 6D shows a similar, triple arrangementwherein control of the drive points and decouplings takes place in ⅓phases. FIGS. 7A-D show in schematic manner, with only drive parts 306a-c, a number of double-action arrangements, wherein it will beunderstood that the arrangement in FIG. 7B corresponds with thataccording to FIG. 5.

The linear drive according to the invention can be used at manylocations. An elevator cage can thus be provided with a number of suchdrives, which engage on vertical fixed shafts. It is noted in thisrespect that, where mention is made in the foregoing and in the appendedclaims of driving a shaft, this term is intended in relative sense.

Other uses can be in mixing consoles of audio equipment, set-ups foropening windows, valve actuators, catering equipment, micro-drives,electrical locks (optionally with spring resetting), electrical bedadjustment, diverse (para)medical applications, fluid dispensing,scanners, printers and other computer equipment, valve control for fuelengines, photocopiers, printing equipment, production automation,aviation and space travel, robot technology, defence industry, brakes,clamps, clutches, diverse household and other consumer appliances and soon.

The linear drive according to the invention can be fitted at manylocations due to the compact embodiment.

The invention is of course not limited to the shown and describedpreferred embodiments, but extends particularly to any possiblecombination of these embodiments, and extends generally to anyembodiment which falls within the scope of the appended claims as seenin light of the foregoing description and drawings.

1. Method for relative driving of bodies on the basis of electromagneticor piezo-electrical conversion of electricity into force and/ormovement, characterized in that use is made of intermediate bodies forthe conversion into mechanical energy.
 2. Method as claimed in claim 1,characterized in that these intermediate bodies can be integrated withtheir surroundings, separated by resilient parts.
 3. Method as claimedin claim 1 or 2, characterized in that the electrical energy is at leastpartially converted into buffered mechanical energy using theseintermediate bodies before it is generated to the output shaft. 4.Method as claimed in any of the foregoing claims, characterized in thatthe intermediate bodies are suspended in buffers, for instance springs,whereby they will want to occupy a preferred position.
 5. Method asclaimed in any of the foregoing claims, characterized in that theintermediate bodies are suspended such that they can store kineticenergy.
 6. Method as claimed in claim 5, characterized in that theintermediate bodies represent an amount of energy dependent on speed andposition.
 7. Method as claimed in any of the foregoing claims,characterized in that a plunger or (part of) a disc is as intermediatebody which is arranged round or inside a body for driving.
 8. Method asclaimed in claim 7, characterized in that an intermediate body isactuated in the non-clamping direction, whereby energy is bufferedbefore it is transferred to the body for driving.
 9. Method as claimedin any of the foregoing claims, characterized in that when anintermediate body is actuated a reaction force is generated onto one ormore other bodies.
 10. Method as claimed in any of the foregoing claims,characterized in that when the electromechanical or electromagneticconverter is energized a force not dependent on position is obtainedbetween two or more (parts of) intermediate bodies.
 11. Method asclaimed in claim 9 or 10, characterized in that when an intermediatebody is actuated a reaction force is generated onto another intermediatebody, wherein this force is transferred to the body for driving. 12.Method as claimed in any of the foregoing claims for coupling theintermediate body and the body for driving, characterized in that theenergy-transferring element consists of a plurality of componentsmovable independently of each other.
 13. Method as claimed in claim 12,characterized in that the energy-transferring element consists of onecomponent which distinguishes resiliently pivoting elements.
 14. Methodas claimed in claim 12 or 13, characterized in that theenergy-transferring element does not slip or roll relative to theencasing bodies in the direction of energy transfer.
 15. Method asclaimed in claim 12, 13 or 14, characterized in that the direction ofpossible energy transfer changes due to a change in position of theenergy-transferring elements.
 16. Method as claimed in claim 15,characterized in that in a neutral position the energy-transferringelement can move freely over the body for driving, but that the geometrycauses tilting through angular displacement, and thus transfer ofenergy.
 17. Method as claimed in any of the foregoing claims forcoupling the intermediate body and the body for driving, characterizedin that the energy-transferring element clamps in both directions. 18.Method as claimed in claim 17, characterized in that thisenergy-transferring element can be releasing or clamping in twopositions relative to the body for driving.
 19. Method as claimed inclaim 17 or 18, characterized in that actuation is possible betweenthese two positions.
 20. Method as claimed in any of the foregoingclaims, characterized in that the force, speed and power can be variedby means of the manner of actuation.
 21. Linear drive assembly for ashaft or other elongate body, comprising engaging means forco-displacing engagement of the shaft and the like, as well asdisplacing means forming a moving whole with the engaging means fordisplacing the engaging means in driving direction between anon-engaging or slipping position and an engaging or shaft-co-displacingposition, further comprising means for displacing the displacing meansin driving direction.
 22. Drive assembly as claimed in claim 21, whereinthe displacing means are adapted to exert a pushing force on theengaging means in the driving direction.
 23. Drive assembly as claimedin claim 21 or 22, wherein the engaging means comprise shoes providedwith engaging surfaces which engage the shaft, as well as preferablyresilient arms which extend radially counter to the driving direction ofthe shoes and which connect the shoes to the displacing means.
 24. Driveassembly as claimed in claim 23, wherein the arms are connected movably,in particular rotatably or tiltably, to the displacing means.
 25. Driveassembly as claimed in claim 23 or 24, wherein the shoes are at alltimes held close to the shaft, preferably by means of a belt.
 26. Driveassembly as claimed in any of the foregoing claims, further providedwith means, preferably at least one electromagnet, for displacing thedisplacing means.
 27. Drive assembly as claimed in claim 26, wherein thedisplacing means and drive means are received in a holder, such as ahousing, which is disposed slidably in shaft direction.
 28. Driveassembly as claimed in claim 26, wherein said means comprise aferromagnetic end plate in combination with an electromagnet.
 29. Driveassembly as claimed in claim 26, wherein said means comprise a (freelymoving) coil in a permanent magnetic field.
 30. Drive assembly asclaimed in claim 27, further comprising means for moving back theholder, in particular the displacing means, counter to the drivedirection relative to the shaft.
 31. Drive assembly as claimed in claim28, wherein the means for moving back comprise a spring.
 32. Driveassembly as claimed in claim 28, wherein the means for moving backoperate electromagnetically.
 33. Drive assembly as claimed in any of theforegoing claims, further provided with relatively stationary means forretaining the shaft in a return direction.
 34. Drive assembly as claimedin claim 31, wherein the retaining means comprise shoes and armscomparable to the drive means.
 35. Drive assembly as claimed in claim32, wherein the retaining means act passively on the shaft, whereinmeans are present for de-activating the retaining means, preferablyelectromagnetic means.
 36. Drive assembly as claimed in claim 33,wherein the means for de-activating comprise means for reducing thecontact pressure of the shoes against the shaft.
 37. Device comprisingtwo drive assemblies as claimed in any of the foregoing claims, whereinthe drive assemblies are disposed for moving the shaft in oppositedirections.
 38. Device as claimed in claim 35, further provided withmeans for de-activating the engaging means, preferably electromagneticmeans, during a return stroke of the shaft and the like.
 39. Device asclaimed in claims 35 and 36, wherein the means for de-activating theengaging means are placed outside the holder according to claim
 7. 40.Device as claimed in any of the foregoing claims, wherein the means forde-activating the engaging means preferably act electromagnetically inone direction and by means of a spring in another direction.
 41. Deviceas claimed in claim 35, wherein the holder is buffered in two directionsby a spring.
 42. Device as claimed in claim 35, wherein the drive meansare buffered in both directions by springs.
 43. Device comprising two ormore devices as claimed in claim 35, which are actuated in mutuallyadapted phases in order to provide a more uniform movement.
 44. Deviceas claimed in any of the foregoing claims, wherein the actuation of thedrive means is controlled such that a homogeneous, prescribed force ordisplacement is realized.
 45. Linear drive assembly for a shaft or otherelongate body, comprising engaging means for co-displacing engagement ofthe shaft and the like, further comprising controllableelectromagnetically acting means for displacing the engaging means indriving direction.
 46. Drive assembly as claimed in any of the foregoingclaims, further comprising controllable electromagnetically acting meansfor releasing the drive means from the shaft.
 47. Drive assembly asclaimed in any of the foregoing claims, further comprising controllableelectromagnetically acting means for fixing the shaft.
 48. Device asclaimed in any of the foregoing claims, further provided with a positionsensor.
 49. Device as claimed in any of the foregoing claims, furtherprovided with a position sensor integrated into the shaft.
 50. Device asclaimed in any of the foregoing claims, further comprising electronic orother means for actuating the engaging and drive means according to theforegoing claims, comprising analog, digital, fuzzy logic or a neuronalnetwork, or a combination of these means.
 51. Device as claimed in anyof the foregoing claims, wherein electromagnetic means are replaced byan alternative, preferably piezo-actuators.